Three collaborative population based studies of skin cancer are proposed which will focus upon ultraviolet light, dietary factors, biochemical markers and other known or suspected epidemiologic risk factors and their interrelationship. Cases and controls will be obtained from the 6 counties of Southeastern Arizona. Two of the proposed studies will use a case-control design, with cases defined by a pathologically confirmed diagnosis of cutaneous basal or squamous cell carcinoma for one study and cases defined by a pathologically confirmed diagnosis of melanoma for the second study. For each case, 2 persons from the population of these counties, frequency matched by age, sex, ethnic origin, and geographic region, will be selected as controls using random digit dialing. Due to the similar age and sex distribution for melanoma and nonmelanoma (i.e. basal and squamous cell carcinoma) cases, a large proportion of persons selected as controls for one study are anticipated to be matched and used as controls for the second case-control study. The third proposed study will use a prospective cohort design and include all cases of nonmelanoma included in the first case- control study described above plus added subjects with 1 or more prior nonmelanoma skin cancers. Cohort subjects will have had their nonmelanoma skin cancer pathologically confirmed completely removed and will be followed for the diagnosis of subsequent skin cancers. All subjects will be interviewed at the time on study. Nonmelanoma subjects will also be interviewed at 12 month intervals. Blood and tissue specimens will be collected, processed and stored for all study subjects at the time on study. These specimens will be kept in storage for analysis during 1989- 90 (year 4 of this project) and after the interview, data has been analyzed. Analyses of specimens will include retinyl palmitate, beta-carotene and other micronutrients identified from analysis of dietary intake data obtained during interview. A four year total duration for all studies is planned and includes analysis and preparation of manuscripts.